During operation of a vehicle, electric charge can be conducted to earth through the tires provided that the tires have a sufficient level of conductivity. Without this conductivity, a moving vehicle is susceptible to the build-up of static electric charge which can negatively affect electronic circuitry, interfere with radio reception, create unwanted sparks, and/or cause personal discomfort. Tires are constructed of natural and synthetic rubbers which are electrical insulators. Accordingly, conductive materials (e.g., carbon black mix) are commonly introduced into a tire to increase its electrical conductivity and thereby avoid the build-up of static electric charge. For example, in a method disclosed in U.S. Pat. No. 6,183,581, a carbon black mix in a volatile liquid is poured into through-holes in a central region of a tire tread. When the volatile liquid evaporates, the carbon black mix is left inside the holes to create electrically conducting bodies which form electrical bridges between the tire's rolling surface and its carcass. The entire disclosure of this patent is hereby incorporated by reference.